| 1 | package slides |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "fmt" |
| 6 | "testing" |
| 7 | ) |
| 8 | |
| 9 | // TestSnapshotWrittenAtBoundaryAndUsedOnOpen: a deck that crosses the |
| 10 | // cadence boundary gets exactly one snapshot, openDeck replays only the |
| 11 | // tail after it, and the document it produces is the same document the |
| 12 | // whole log produces. |
| 13 | // |
| 14 | // The last clause is the one that matters. A snapshot is an accelerator |
| 15 | // and derived data (models.go's DeckSnapshot); the moment it is not |
| 16 | // byte-for-byte the same deck, it is a second, wrong copy of the truth. |
| 17 | func TestSnapshotWrittenAtBoundaryAndUsedOnOpen(t *testing.T) { |
| 18 | d := testDB(t) |
| 19 | a, _, err := newApp(d, Config{Env: EnvDevelopment, Logger: quietLogger()}) |
| 20 | if err != nil { |
| 21 | t.Fatalf("newApp: %v", err) |
| 22 | } |
| 23 | t.Cleanup(func() { a.Close() }) |
| 24 | ctx := context.Background() |
| 25 | |
| 26 | owner, _, err := ensureUser(ctx, d.G, "paul@example.test") |
| 27 | if err != nil { |
| 28 | t.Fatalf("ensureUser: %v", err) |
| 29 | } |
| 30 | actor := actorFor(owner) |
| 31 | |
| 32 | row, err := a.createDeckRow(ctx, owner, "Long deck", defaultTheme) |
| 33 | if err != nil { |
| 34 | t.Fatalf("createDeckRow: %v", err) |
| 35 | } |
| 36 | opening, err := openingOps("Long deck", defaultTheme) |
| 37 | if err != nil { |
| 38 | t.Fatalf("openingOps: %v", err) |
| 39 | } |
| 40 | if err := a.editDeck(ctx, &row, actor, opening, nil); err != nil { |
| 41 | t.Fatalf("editDeck: %v", err) |
| 42 | } |
| 43 | |
| 44 | // One handle for the rest, so this is 200 applies rather than 200 |
| 45 | // full replays — the test is about the boundary, not about how |
| 46 | // slowly a deck can be built. |
| 47 | h, _, err := a.openDeck(ctx, row) |
| 48 | if err != nil { |
| 49 | t.Fatalf("openDeck: %v", err) |
| 50 | } |
| 51 | defer h.Close(ctx) |
| 52 | for row.Seq < snapshotCadence+1 { |
| 53 | batch, err := opsJSON([]op{{"op": "set_meta", "title": fmt.Sprintf("Long deck %d", row.Seq)}}) |
| 54 | if err != nil { |
| 55 | t.Fatalf("opsJSON: %v", err) |
| 56 | } |
| 57 | if _, err := a.applyOps(ctx, h, &row, actor, batch, nil); err != nil { |
| 58 | t.Fatalf("applyOps at seq %d: %v", row.Seq, err) |
| 59 | } |
| 60 | } |
| 61 | if row.Seq != snapshotCadence+1 { |
| 62 | t.Fatalf("the deck is at seq %d, want %d", row.Seq, snapshotCadence+1) |
| 63 | } |
| 64 | |
| 65 | var snapshots []DeckSnapshot |
| 66 | if err := d.G.WithContext(ctx).Where("deck_id = ?", row.ID).Order("seq").Find(&snapshots).Error; err != nil { |
| 67 | t.Fatalf("read snapshots: %v", err) |
| 68 | } |
| 69 | if len(snapshots) != 1 { |
| 70 | t.Fatalf("%d snapshots after %d updates, want exactly 1", len(snapshots), row.Seq) |
| 71 | } |
| 72 | if snapshots[0].Seq != snapshotCadence { |
| 73 | t.Errorf("the snapshot is at seq %d, want %d", snapshots[0].Seq, snapshotCadence) |
| 74 | } |
| 75 | if len(snapshots[0].Bytes) == 0 { |
| 76 | t.Error("the snapshot carries no bytes") |
| 77 | } |
| 78 | |
| 79 | // openDeck replays the tail and nothing before it. |
| 80 | snap, tail, err := a.replayPlan(ctx, row) |
| 81 | if err != nil { |
| 82 | t.Fatalf("replayPlan: %v", err) |
| 83 | } |
| 84 | if snap == nil || snap.Seq != snapshotCadence { |
| 85 | t.Fatalf("replayPlan chose %+v, want the snapshot at seq %d", snap, snapshotCadence) |
| 86 | } |
| 87 | if len(tail) != 1 || tail[0].Seq != row.Seq { |
| 88 | t.Fatalf("replayPlan replays %d updates, want the one at seq %d", len(tail), row.Seq) |
| 89 | } |
| 90 | |
| 91 | // And it is the same deck either way. |
| 92 | want, err := h.JSON(ctx) |
| 93 | if err != nil { |
| 94 | t.Fatalf("read the live view: %v", err) |
| 95 | } |
| 96 | fromSnapshot := viewJSON(t, a, row) |
| 97 | if string(fromSnapshot) != string(want) { |
| 98 | t.Fatalf("opening from the snapshot gives a different deck:\n got %s\nwant %s", fromSnapshot, want) |
| 99 | } |
| 100 | |
| 101 | // Deleting the snapshot loses nothing: the log alone still is the |
| 102 | // deck, which is what makes a snapshot safe to throw away. |
| 103 | if err := d.G.WithContext(ctx).Where("deck_id = ?", row.ID).Delete(&DeckSnapshot{}).Error; err != nil { |
| 104 | t.Fatalf("delete snapshots: %v", err) |
| 105 | } |
| 106 | if fromLog := viewJSON(t, a, row); string(fromLog) != string(want) { |
| 107 | t.Fatalf("opening from the plain log gives a different deck:\n got %s\nwant %s", fromLog, want) |
| 108 | } |
| 109 | } |
| 110 | |
| 111 | // viewJSON opens d the way a request does and returns the core's view. |
| 112 | func viewJSON(t *testing.T, a *app, d Deck) []byte { |
| 113 | t.Helper() |
| 114 | ctx := context.Background() |
| 115 | h, _, err := a.openDeck(ctx, d) |
| 116 | if err != nil { |
| 117 | t.Fatalf("openDeck: %v", err) |
| 118 | } |
| 119 | defer h.Close(ctx) |
| 120 | raw, err := h.JSON(ctx) |
| 121 | if err != nil { |
| 122 | t.Fatalf("read the view: %v", err) |
| 123 | } |
| 124 | return raw |
| 125 | } |
| 126 | |
amadan